I've got a 12ft v-hull aluminum boat that I like to go fishing in. The only motor I've got right now is a Minn Kota 55lb thrust trolling motor. It gets the job done for now. I typically have to drive to the general location I want to fish and then set her in. I want to get an outboard motor, obviously so I can move to further spots on the lake, etc. (I also like to take my daughters out on the boat from time to time, and putzing around with a trolling motor is only so fun after a little bit.) I want to be able to get on plane with the boat... Am I right in thinking a 9.9hp outboard is the way to go with my boat? How should I determine whether I need a 15" vs a 20" shaft length?

I took a trip to Canada last summer and the boats there all had 20-25 hp 15" motors. They were about the same size as yours....Lund was the brand.

We got around pretty good.

measure your transom height, it should be 15" for your boat size...
don't buy a motor unless you can get it repaired close by, I prefer evinrude/Johnson/Yamaha, but that is just me. i lost my mechanic last year, and I have to drive 40 miles for work on my motor.

A lot of the small outboards are single cylinder. I don't like single cylinder outboards(or any other motors). Try to get a twin, and you will enjoy it more. Mine is a 56 year-old Johnson 5.5 Twin and it runs smooth, like top.

Island Jim

15 inch shaft should be right for that boat. 9.9 horse will move you just fine. A 20 would flat scoot on a 12 footer with just you in the boat. If you have 3 people in the boat though you might enjoy the extra power. Up to you. Anything will go faster than what you're doing right now though!

I would said first thing is to see what the boat is rated for. There should be a plate somewhere on the boat that will state what the load limit is as well as what the maximum horsepower is. On a 12 footer v-hull I would said 10 or 15 would probably be the max. But depend on the width and gauge of the hull it could be 20-25.

The plate on the inside of the transom says maximum horsepower is 16 HP and the maximum weight of 684lbs. So I guess that means I know my high end when it comes to horsepower. I guess I'm mainly interested in getting opinions from experienced boaters on whether I need all 15 HP or if 9.9 HP will be plenty. I suppose it would be better to err on the side of more HP so that I know I've got the most power that the boat can handle available for when we have a heavier load in the boat (two adults, etc). Yes?

I think you answer your own question. I use to have a Monark 1436 it were rated for 20hp and I put a 15hp. It were great. But there were time when I wish I had a little more power. So I would said better to have the power and don't needed it than to not have it and need it.

Im going to try not to sound like a prick here, or insult your intelligence. As it warms up our lakes are going to become one of the most dangerous places imaginable for people in little bitty boats. if you're going to put that boat in any public lake be freaking careful, I see rigs like you have with little kids on them and it makes my stomach turn. Know the limitations of that boat and for the love of god be careful. I think we have all been watching the news lately and think it cant happen to me

You make a good point, and I appreciate your honesty and advice to be cautious. Most of my fishing happens at dawn or dusk, so I'm honestly not planning to be out on the water with my boat during "prime time" hours when everyone else is out there with bigger vessels. Additionally, if/when I take any of my daughters out on the boat with me, I am the first one to promote safety and caution. It's fun to get on the water and ride around, but not at the expense of safety and definitely not at the expense of the well-being of anyone in my family. So, thank you again for the urge to be careful! We're definitely on the same page!

Ill add those old tins are rated for 2 stroke motors that are significantly weigh less then the4strokes of today. More stress on the transom and more weight on the back. I'd suggest stepping down to the 9.9. Also you'll find it out right scary once a big boat flies by you with no reguard for you and yours. I suggest running around with150lbs of sand bags b4 you put your kids in.

Have a 1436 as well... its down right dangerous with a 15 hp on it. Ive had way more people and weight in it than I ever should have and power was not something it ever lacked.

How old is the boat? Older boats were not built with 4 stroke motors in mind and many will have issues supporting the weight associated with them. Some of the older 15 ish hp engines weigh 1/2 of what the modern ones do.

What kind of boat is it? Width of the boat has a lot to do with it. If its a wide beam boat I think 9.9 or 10 hp to 15 would be good. If its a narrow I think 5 or so is a much better area.